No one will ever be given blood without it being 'cross matched' to make sure that no reaction occurs. A medical professional would never take a blood group as provided by the patient.
In an emergency there are fluids such as Haemaccel which will be given until the cross matched blood is available. And indeed as a totally last resort, Group 0 can be given, but that would be avoided if at all possible.
Good Morning Good Friday 29th March 2024